Solvent Substitution as a Probe of Gating Processes in Voltage-Dependent Ion Channels

SINGLET OXYGEN INVOLVEMENT IN PHOTOHEMOLYSIS SENSITIZED BY MEROCYANINE‐540 and ROSE BENGAL

“…The slight potentiation of photohemolysis (3 to 6%) when D 2 0 is added after illumination is not significant compared to experimental error. It may result from errors introduced by solution replacement, scatter in the data, toxic contaminants sometimes found in D 2 0 (Schauf, 1983), or it may be a real effect of D 2 0 on the ion leak pathway. Its origin cannot be discerned from the present data.…”

Insensitivity of activation delays in potassium and sodium channels to heavy water in Myxicola giant axons.

“…Inactivation of open sodium channels during maintained step depolarizations, as well as sodium inactivation produced by changes in initial conditions (pre-pulses), are also slowed by D20 (Schauf& Bullock, 1980). In contrast, the intramembrane charge movements associated with Na+ channel activation are not significantly affected by D20 (Schauf & Bullock, 1981), although their immobilization, which is generally agreed to be related to Na+ inactivation (Armstrong & Bezanilla, 1977;Nonner, 1980), occurs more slowly following solvent substitution (Schauf, 1982). The lack of a D20 effect on Na+ gating current in the presence of slowed ionic kinetics implies that most, if not all, of the measured intramembrane charge movement occurs in transitions between one or more of the non-conducting states which precede Na+ channel opening.…”

Water proton transfer and hydrogen bonding in ion channel gating

“…there have been a number of physiological studies, by Schauf and coworkers (working with Myxicola) and Alicata, et al (working with crayfish) (63)(64)(65)(66)(67). The gist of the results is that there are two major sections of the gating sequence: the initial gating current is not affected significantly by deuterium substitution, but the final opening step is.…”